RATIO OF METASTATIC LYMPH NODES VS. RESECTED LYMPH NODES (N-RATIO) HAS PROGNOSTIC IMPLICATIONS IN GASTRIC CANCER

ABSTRACT BACKGROUND: Lymph node status is vital for gastric cancer (GC) prognosis, but the conventional pN stage may be limited by variations in lymphadenectomy and stage migration. The N-Ratio, which assesses the ratio of metastatic to resected lymph nodes, emerges as a promising prognostic tool. AIMS: To assess N-Ratios prognostic value in GC, particularly in patients with <25 resected lymph nodes. METHODS: Patients who underwent gastrectomy with curative intent for GC were retrospectively evaluated. The N-Ratio categories were determined using the ROC curve method, and the area under the curve (AUC) was used as a measure of performance in predicting recurrence/death. RESULTS: A total of 561 GC patients were included in the study, 57% had pN+ status, and 17.5% had <25 resected lymph nodes. N-Ratio, with a mean of 0.12, predicted survival with 74% accuracy (AUC=0.74; 95%CI 0.70–0.78, p<0.001). N-Ratio categories included: N-Ratio 0 (43%); N-Ratio 1 (12.3%); N-Ratio 2 (31.6%); and N-Ratio 3 (13.2%). Disease-free survival (DFS) varied among all N-Ratio groups, with N-Ratio 3 showing worse survival than pN3 cases (DFS=21.8 vs. 11 months, p=0.022, p<0.05). In cases with <25 resected lymph nodes, DFS was not significantly worse in N-Ratio 0 (68.8 vs. 81.9%, p=0.061, p>0.05) and N-Ratio 1 (66.2 vs. 50%, p=0.504, p>0.05) groups. The DFS of N-Ratio-0 cases with <25 lymph nodes was similar to N-Ratio 1 cases. CONCLUSIONS: N-Ratio influenced survival in GC patients, especially in advanced lymph node disease (N-Ratio 3). Considering that N-Ratio does not impact pN0 cases, individualized prognosis assessment is essential for patients with <25 resected lymph nodes.


A QUEDA DA PRESSÃO PORTAL APÓS DESVASCULARIZAÇÃO ESOFAGOGÁSTRICA E ESPLENECTOMIA INFLUENCIA A VARIAÇÃO DO CALIBRE DAS VARIZES E AS TAXAS DE RESSANGRAMENTO NA ESQUISTOSSOMOSE NO SEGUIMENTO EM LONGO PRAZO?
Does the drop in portal pressure after esophagogastric devascularization and splenectomy variation of variceal calibers and the rebleeding rates in schistosomiasis in late follow-up?
Walter de Biase SILVA-NETO 1 , Claudemiro QUIRESE 1 , Eduardo Guimarães Horneaux de MOURA 2 , Fabricio Ferreira COELHO 3 , Paulo HERMAN 3 ABSTRACT -Background: The treatment of choice for patients with schistosomiasis with previous episode of varices is bleeding esophagogastric devascularization and splenectomy (EGDS) in association with postoperative endoscopic therapy.However, studies have shown varices recurrence especially after long-term follow-up.Aim: To assess the impact on behavior of esophageal varices and bleeding recurrence after post-operative endoscopic treatment of patients submitted to EGDS.Methods: Thirty-six patients submitted to EGDS portal pressure drop, more or less than 30%, and compared with the behavior of esophageal varices and the rate of bleeding recurrence.Results late post-operative varices caliber when compared the pre-operative data was observed despite an increase in diameter during follow-up that was controlled by endoscopic therapy.

Conclusion
variceal calibers when comparing pre-operative and early or late post-operative diameters.
The comparison between the portal pressure drop and the rebleeding rates was also not

Central Message
Lymph node status is crucial for determining the prognosis of patients with GC, particularly in those with more advanced cancers, in whom metastasis may occur more frequently.In this regard, gastrectomy with D2 lymphadenectomy is the gold-standard treatment for patients with locally advanced gastric cancer (GC).Some investigators have proposed using the N-Ratio, namely the ratio between metastatic lymph nodes (LNs) and the total number of LNs examined, as a new prognostic indicator for GC, even in the case of limited LN dissection.The surgical specimens were evaluated by histopathological criteria according to the College of American Pathologists protocol (CAP -Cancer Protocols and Checklists), as already performed in our routine.
The follow-up was performed after surgery every three months in the first year and every six months in subsequent years.This study was approved by the hospital's Ethics and Research Committee and is registered at Plataforma Brasil (a national and unified database of records and research involving human beings) (CAEE: 54787422.3.0000.0068).

N-Ratio classification
The N-Ratio was calculated for each patient according to the following formula: N-Ratio=number of positive lymph nodes/number of resected lymph nodes.
The area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the metric performance of the N-Ratio in predicting recurrence or death.The optimal cutoff value was determined by maximizing Youden's index (sensitivity + specificity -1) to distinguish N-Ratio 1 and N-Ratio 2. To define the N-Ratio category 3, the cutoff value was obtained in which the specificity reached 70%.The predictive capacity of the N-Ratio categories was tested by Kaplan-Meier survival method analysis.

Statistical analysis
Data were described using the mean (with SD, standard deviation) and median (with IQR, interquartile range) quantitative variables, and frequency for qualitative variables.
The differences between the groups were analyzed using the chi-square test for nominal variables and t-test, ANOVA, or Kruskal-Wallis test for continuous variables.
Survival was estimated by the Kaplan-Meier method, and the log-rank test was used to identify statistical differences between groups.Disease-free survival (DFS) was calculated from the date of surgery until the date of recurrence or death from any cause.Alive patients were censored at the date of the last follow-up.The Cox proportional hazards model was used to identify risk factors related to survival.Significant variables in the univariate analysis were included in the multivariate model to verify those independently associated with survival outcomes.The results were reported as hazard ratios (HRs) with 95% confidence intervals (CI).
All analyses were performed using SPSS version 20.0 (SPSS, Chicago, IL, USA).Results were considered statistically significant when p<0.05.

RESULTS
A total of 561 patients who met the eligibility criteria were included in the study.The clinicopathological and surgical data for these patients are summarized in Table 1.
The median number of resected LNs was 41.2 (range 4-115), and 57% of the patients had lymph nodal metastasis.In addition, 17.5% of patients had fewer than 25 resected LNs.Most cases were staged as pTNM III (44.7%), and 56.7% of patients received preoperative or adjuvant chemotherapy (91 and 273 cases, respectively).
The N-Ratio was calculated for each patient, and the median value was 0.12.The accuracy of N-Ratio in predicting INTRODUCTION G astric cancer (GC) is one of the most common neoplasms worldwide, ranking fifth in incidence and fourth in mortality among all cancers 9,28 .Lymph node status is crucial for determining the prognosis of patients with GC, particularly in those with more advanced cancers, in whom metastasis may occur more frequently.In this regard, gastrectomy with D2 lymphadenectomy is the goldstandard treatment for patients with locally advanced GC 2,6,14 .
In GC, lymphatic dissemination is more prevalent than hematogenous spread, which justifies lymphadenectomy during surgery 5 .Lymphadenectomy can be D1, in which the lymph nodes closest to the stomach are resected, or D2, in which the resection is expanded through the vessels that supply the stomach 27 .D2 lymphadenectomy is associated with better survival 25,27 , although it is associated with higher rates of postoperative complications especially in older, high-risk patients with comorbidities 14,23,26 .
Despite the reliability and simplicity of the TNM classification, it has some issues related to the correct number of lymph nodes (LNs) to be resected for an accurate staging.The Union for International Cancer Control/American Joint Committee on Cancer (UICC/AJCC) recommends that at least 15 LNs could be examined for correct staging, while the Japanese Gastric Cancer Association (JGCA) recommends that more than 25 lymph nodes is ideal for correct staging 11,12,17 .Some studies also suggest that this classification is involved in problems with stage migration, related to the Will Rogers Phenomenon 3,8 , which can lead to some patients being incorrectly staged, as the patient's stage may vary due to lymph node involvement 4,5,29 .
In order to reduce stage migration, some investigators have proposed using the N-Ratio, namely the ratio between metastatic LNs and the total number of LNs examined, as a new prognostic indicator for GC, even in the case of limited LN dissection 7,18,21,31 .
Although some researchers have reported that N-Ratio is an independent prognostic factor, to date there is no N-Ratio system considered standard for use 13,15,20,21,30 .Different N-Ratio systems with different cutoff values had been proposed 20,29,31 , and there are controversies as to whether its applicability would be restricted to cases with LN yield, patients after neoadjuvant chemotherapy (CMT), or remnant gastric cancer 21,24,25 .
Thus, the aim of this study was to investigate the prognostic value of N-Ratio in patients with GC after curative surgical treatment.We also evaluated the influence on survival in patients with fewer than 25 resected LNs.

METHODS
Patients with GC who underwent surgical procedures at our Institution between 2009 and 2020 were evaluated from our prospectively collected database.
Patients were selected for the study according to the following eligibility criteria: All patients underwent gastrectomy with lymphadenectomy according to the guidelines of the JGCA 4 .The eighth edition of the TNM classification was used for staging.

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ABCD Arq Bras Cir Dig 2024;37:e1824 DFS was evaluated using a ROC curve, and the AUC was used to determine its accuracy, as presented in Figure 1.The N-Ratio had an accuracy of 74% (AUC=0.741,95%CI 0.698-0.783,p=0.022).Based on sensitivity and specificity values, the patients were classified into the following N-Ratio groups using the cutoff values: N-Ratio 0: 0%; N-Ratio 1: 0-5%; N-Ratio 2: 6-33%; N-Ratio 3: >34%.The established cutoff values and the distribution of patients in the N-Ratio categories are presented in Table 2.
Clinicopathological characteristics in relation to the N-Ratio groups are presented in Table 3.The frequency of total gastrectomy and D1 lymphadenectomy was higher in the N-Ratio 3 group.Furthermore, larger tumor size, diffuse histological type, poorly differentiated histology, and advanced pT and pTNM stage were also more common in the N-Ratio 3 category.Lower frequency of lymphatic, venous, and perineural invasion were observed in the N-Ratio 0 category.
The groups also differed regarding the mean number of resected lymph nodes, with the highest frequency of cases with fewer than 25 LNs in the N-Ratio 3 group (25.7% of cases).The N-Ratio 1 category presented the highest frequency of cases, with at least 25 resected LNs (94.2% of cases).

Survival analysis
The median follow-up for the entire cohort was 47.1 months (mean = 48.2).During the follow-up, 160 (28.5%) patients had disease recurrence, and 204 (36.4%) died.The estimated 5-year DFS rate for the entire cohort was 57.4%.
The curves of all N-Ratio categories differed from each other (Figure 2).N-Ratio-0 patients had better survival compared to N-Ratio 1 (p=0.005);while N-Ratio-1 cases had better survival compared to patients classified as N-Ratio 2 (p=0.007).In turn, N-Ratio-3 GC had poorer survival compared to the N-Ratio 2 group (p<0.001).ABCD Arq Bras Cir Dig 2024;37:e1824 When compared to the classic staging pN stage, there was no statistical difference between the DFS of N-Ratio 1 and pN1 group (p=0.650), and between N-Ratio 2 and pN2 group (35.8 vs 35.7 months, respectively; p=0.998).Nevertheless, the DFS in the N-Ratio 3 category was worse compared to pN3 group (p=0.022).The median survival of the N-Ratio 3 and pN3 was 11.1 and 21.8 months, respectively.

Survival according to the number of resected lymph nodes: <25 and ≥25 LNs groups
Survival data for the N-Ratio and pN categories stratified by the number of LNs are shown in Table 4.There was no significant difference between categories when comparing cases with <25 LNs and those with ≥25 LNs.However, a tendency toward better survival was observed in N-Ratio-0/pN0 patients with ≥25 resected LNs compared to <25-LNs cases (Figure 3).
Survival data for cases with <25 and ≥25 LNs, comparing the N-Ratio and pN categories with each other, are presented in Table 1.
In the analysis of risk factors associated with DFS (Table 2), American Society of Anesthesiology (ASA) III/IV, total gastrectomy, pT3/T4 stage, and advanced N-Ratio category were independent factors associated with worse survival.Stepwise regression analysis included all the statistically significant prognostic factors by univariate analysis (Table 6).

DISCUSSION
The present study was developed with the objective of evaluating the prognostic meaning of the N-Ratio classification in patients with GC treated with curative intent.N-Ratio can in fact be used as an alternative prognostic tool to better stage patients with GC.In addition, the prognostic value of N-Ratio based on the numbers of resected LNs (<25 or ≥25) was also evaluated.
We found that the categories determined by N-Ratio are related to independent factors associated with survival, which can lead to a better distinction between patients with a more extent lymph nodal stage and a more deteriorated prognosis.In addition, we could see a possibility to better stage N-Ratio-0 patients when stratified in groups with <25 resected LNs and ≥25 resected LNs.
N-Ratio has been indicated as an effective prognostic tool in several Western and Japanese series due to its capacity to better discriminate subsets of patients with similar prognosis and the ability to reduce the risk of stage migration 13,15,17,[19][20][21][29][30][31] .
Some researchers only analyzed fragments of the population, as the study conducted by Jiang et al. 15 , who excluded patients with metastasis; for instance, Xu et al. 29 and Bando et al. 1 only considered D2 cases.Conversely, several other researchers 13,17,20,22,30,31 , including us, evaluated patients who underwent gastrectomies with curative intent associated with D1 and D2 lymphadenectomy.Furthermore, we could    analyze in our study an average of 41.2 resected LNs, which is a noteworthy parameter considering that previous research reported values ranging from 10 to 51 LNs 1,7,13,15,17,20,22,30,31 .
Concerning GC, different N-Ratio cutoffs have been proposed.In an 1,853 multicentric study, Marchet et al. 20,21 adopted the following N-Ratio cutoffs: 0%, 1 to 9%, 10 to 25%, and >25%, which was obtained based on log-rank test and the Martingale residual analysis.The same cutoffs of Marchet et al. 21were used in Xu et al. 29 analysis, with 906 GC patients.Alternatively, in a study on 351 patients, Yamashita et al. 31 selected four different N-Ratio cutoff values: 0%, 0 to 20%, 21 to 30%, and >30%, and the cutoff point survival analysis was the method used to determine these cutoffs.Based on the ROC curve and the AUC, we could evaluate the metric performance of the N-Ratio in predicting recurrence or death.Finally, we could propose the following cutoff values: 0%, 1 to 5%, 6 to 33%, and >34%.As we can observe, these values differ from those usually found in current literature and, therefore, can be seen as an alternative to future research.
Retrospective analyses of patients who underwent gastrectomies, such as those by Marchet et al. 20,21 and Xu et al. 29 , have shown that the N-Ratio can be used as an independent prognostic factor in all cases, including those with few resected LNs (<15 LNs), when comparing survival to TNM staging.However, authors of other research, such as the one conducted by Mullaney et al. 22 , have suggested that the accuracy of N-Ratio in staging may be compromised when fewer than 15 LNs are removed during resection.This highlights the dilemma and emphasizes the need for future research to consider the amount of LNs to be resected carefully.In comparison with this other analysis, in this study we divided patients in those with <25 LNs and ≥25 LNs, as recommended by JGCA, seeking to find relevance and measure the applicability of N-Ratio even in less extensive LNs resections.
Indeed, this debate around the application of the N-ratio in relation to the average of recovered LNs is particularly important, as the TNM system does not consider lymph nodes that may have the potential to become cancerous, leading to inaccurate staging in cases with fewer resected structures.
Our findings underline this ability of N-Ratio to better stage patients with GC, mainly for those with a worse prognosis, when compared to the stage provided for pN, as we could see the results of median DFS of N-Ratio 3 vs.pN3 (DFS=11.1 vs. 21.8months, p=0.022, p<0.05).
Taking this into consideration, this series not only corroborates the superiority of N-Ratio above the pN staging system as an alternative prognostic tool to better stage patients with GC, but also has a greater capacity to benefit patients with a more deteriorated prognosis, allowing a better treatment management 16 .
Interestingly, even with the difference between N-Ratio 3 and pN3, we observed no differences in survival between N-Ratio 1 vs pN1 and N-Ratio 2 and pN2 groups.This suggests that the N-Ratio was able to reclassify patients who would be understaged by the pN classification.
It should be noted that when submitted to statistical analysis, all the DFS curves of N-Ratio were different from each other (p<0.05),which reinforces the cutoffs previously proposed, ensuring statistical difference between all the N-Ratio groups evaluated.Besides, most of the research compared in this study also presented statistical difference between the survival curves 13,16,17,20,30,31 .
We divided the N-Ratio groups of our cohort into those with fewer than 25 LNs, or ≥25 resected LNs, as recommended by JGCA 14 .17.5% of the patients presented fewer than 25 resected LNs, and while N-Ratio 1 had the greater number of resected lymph nodes (94.2% of patients ≥25 LNs), N-Ratio 3 presented the worst rate (74.3% of patients >25 LNs).This low amount of resected LNs is certainly linked to the more deteriorated prognosis of patients in the N-Ratio 3 group.
Noteworthily, we found significance difference in DFS in N-Ratio 0 when stratified by number of LNs (<25 vs. ≥25 LNs).Moreover, the N-Ratio 0 <25 LNs showed a survival comparable to the N-Ratio 1 (50.3 vs. 46.5 months, respectively), suggesting an indisputable worse prognosis of the group with fewer resected LNs.This observation may be relevant because the indication of adjuvant chemotherapy is based on the TNM stage.Thus, patients pN0 with fewer resected lymph nodes may be suitable to adjuvant chemotherapy.
Most importantly, these values imply that the N-Ratio 0 group was likely understaged and the patients classified as such may instead turn out to be N-Ratio 1 or N-Ratio 2. This raises concerns regarding the adequacy of LNs dissection in the N-Ratio 0 group, considering that, in cases in which there are no positive LNs, patients are automatically assigned to this group.Furthermore, given the limited number of LNs examined, the likelihood of underdiagnosis is significantly increased 10 .
As for the group with ≥25 LNs, in Table 5 we demonstrate that only the comparison between N-Ratio 3 and pN3 was statistically significant (11.0 vs. 30.0,p=0.021, p<0.05).Taking this into consideration, we can presume that the lack of statistical significance in the other comparisons may be attributed to the smaller sample size, as compared to N-Ratio 3 and pN3, and the superior prognostic ability of N-Ratio in predicting poorer outcomes.
It should be noted that at the Cancer Institute of the State of São Paulo, the center where all patients in this study were operated on, it is routine to perform extended lymphadenectomy, and it is hypothesized that the statistical values of N-Ratio would be even more significant for centers that operate with smaller lymph node resections.
The present study has some limitations.This is a retrospective research, in which we evaluated patients based on the experience of a single center.One of the main limitations is the lack of standardization in the cutoffs of the N-Ratio, which have been different in most studies in the literature, as well as the number of LNs that should be resected to obtain a viable and prognostic stage 21 .In the present study, we determined the N-Ratio categories based on the cutoff values determined by ROC curve.Furthermore, although some researchers state that the prognostic impact of the N-Ratio is restricted to patients with inadequate lymph node dissection, in this study it was not possible to assess the influence of the N-Ratio on cases with fewer than 15 LNs.In this case, although evaluating patients with fewer than 25 LNs, the number of patients was limited for some analyses.In fact, the mean number of lymph nodes in our study was 41.2, and D2 lymphadenectomy was performed in 85.6% of cases -which is higher than most studies.This may explain why we did not find significant differences between all N-Ratio categories when stratified by the number of LNs (25 LNs).
Possibly, if applied only in D1 cases, or in a larger cohort of patients with <25 LNs, some differences may be evidenced -which would possibly be those who would most benefit from prognostic determination by applying the N-Ratio.

CONCLUSIONS
N-Ratio was an independent factor associated with survival in GC patients, being able to stratify especially those with more advanced lymph node disease (N-Ratio 3).As the N-Ratio does not weigh pN0 cases, an individualized prognosis index should be considered in those with a lymph node yield of less than 25.

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instagram.com/revistaabcd/twitter.com/revista_abcdfacebook.com/Revista-ABCD-109005301640367linkedin.com/company/revista-abcdEditorial Support: National Council for Scientific and Technological Development (CNPq).1Arq Bras Cir Dig 2024;37:e1824 Perspectives N-Ratio was an independent factor associated with survival in GC patients, being able to stratify especially those with more advanced lymph node disease (N-Ratio 3).As the N-Ratio does not weigh pN0 cases, an individualized prognosis index should be considered in those with a lymph node yield of less than 25.

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Figure 1 -Receiver operating characteristic curve and the area under the curve (AUC) for N-Ratio.

Figure 2 -
Figure 2 -Survival curves of 561 patients according to the N-Ratio categories and comparison of the N-Ratio groups with the pN stage.

Table 1 -
Clinicopathologic and surgical characteristics of 561 patients with gastric cancer.

Table 2 -
Cutoff values and distribution of 561 patients in N-Ratio groups.
AUC: area under the curve.

Table 3 -
Clinicopathological characteristics of gastric cancer of 561 patients according to the N-Ratio categories.

Table 4 -
Disease-free survival of 561 patients based on N-Ratio classification and N stage according to the number of resected lymph nodes.

Table 5 -
Disease-free survival rates of 561 patients according to the number of resected lymph nodes for N-Ratio and pN stages.
nr: not reached; LN: Lymph node.RATIO OF METASTATIC LYMPH NODES VS.RESECTED LYMPH NODES (N-RATIO) HAS PROGNOSTIC IMPLICATIONS IN GASTRIC CANCER 5/8

Table 6 -
Univariate and multivariate analysis for disease-free survival of 561 gastric cancer patients.